Anyone have thoughts about the fuel injection thing or whatever? and brakes info?

I did notice one thing on my brakes...the big round part that you see on disc brakes (I'm not sure if that part is called the disc or not - I know nothing about brakes) on my car are yellow. (I have an LX so only the front two). They aren't completely yellow, but there are visible yellow marks/streaks etc. Looks like some kind of dirt or dust or something....is that an indication that I may need to change my pads? If I do have to replace my pads, what kind should I get?